This invention relates generally to the production of maize commonly known in the United States as corn and more particularly concerns the development and production of inbred and hybrid semi-dwarf maize with other desired characteristics.
Commercial hybrid maize normally grows to a height of nine to ten feet with each plant having either one or two ears. The ear normally grows about one-third the way up the plant or about three feet from the ground. Consequently the maize plant, while providing a large ear has a substantial leaf and stalk structure and a considerable mechanical stability problem in that the heavy ear is about three feet from the ground with six feet of stalk and the tassels extending above that. In the past, efforts have been made to develop strong branching of secondary roots in maize to help alleviate this problem. While these efforts have improved the mechanical stability of maize considerably, heavy wind storms or rain will still wreak havoc in a field of maize.
Accordingly, one of the objects of this invention is to provide a method to reduce the height of the maize plant thereby improving the mechanical stability of the plant.
While great gains have been made in the use of hybrid maize in the productivity and yield per acre, over that of inbred maize, further substantial gains due to hybrid vigor are not anticipated. Consequently, efforts must be directed to drastically changing the characteristics of the commercial maize plant by genetic or environmental manipulation.
Hence, one of the objects of this invention is to significantly increase the yield per acre of maize. For example, in the Apr. 17, 1974 edition of The Wall Street Journal, the article entitled "In Search of Superbean", it was pointed out that soybeans could not easily be hybridized and therefore fell far behind corn in productivity increase. During the period from 1950 to 1973, soybeans increased in productivity from 21.8 to 27.8 bushels per acre while corn increased from 38.4 to 91.4 bushels per acre.
Unfortunately, while hybrid vigor has resulted in great increases in yield it normally causes a similar great increase in height of the maize plant due to the recessive nature of dwarf genes. Thus, to produce recessive dwarf hybrid seeds, care must be taken to shield the plant from possible normal pollen carried from neighboring fields.